Low Scaling Quantum Chemistry (LSQC) Program

News: LSQC 3.0 is available (January 19, 2025)!

Table of Contents

1. Introduction

2. Documentation and License

3. Modules

4. References

5. Contacts

Introduction

Low Scaling Quantum Chemistry (LSQC) program (No. 2006SR09617) is a quantum chemistry package for linear or low scaling electronic structure calculations of large systems, which was developed by the research group of Professor Shuhua Li and Professor Wei Li in Nanjing University. The original version is LSQC-1.0 published on April 20, 2006, and the current version is LSQC-3.0 published on January 19th, 2025. The LSQC program supports two methods for electronic structure calculations of large systems. The first one is the generalized energy-Based fragmentation (GEBF) method and the other one is the cluster-in-molecule (CIM) local correlation method.

In current version, LSQC has been further developed into a general-purpose quantum chemistry software, capable of energy calculations, structure optimization, and more using traditional quantum chemistry methods (e.g., HF, MP2, etc.). This version supports MPI parallel computing, and some methods also support GPU (including domestic DCU) parallel computing, enabling efficient execution on computing clusters. The latest information of LSQC program can be found via our website at http://itcc.nju.edu.cn/lsqc or the following QR code:

Documentation and License

• To request a binary copy of LSQC program, please complete the LICENSE FORM, and upload its copy (or photo) during the registeration of LSQC program via the following QR Code or the link "LSQC Registeration".

• Download the LSQC Manual (Chinese, English)

Modules

GEBF

In the GEBF approach, the total energy of a macromolecule is directly obtained from the energies of a series of subsystems, which are computed using conventional quantum chemistry methods. This approach provides accurate results for closed-shell systems with localized electrons, such as biomolecules and polymers. For large systems with hundreds or even thousands of atoms, the GEBF-X approach enables full quantum mechanical (QM) calculations at the X level on standard workstations.

Electrostatically embedded subsystems can be calculated at various theoretical levels using existing quantum chemistry programs. Currently, only the Gaussian program is supported for subsystem calculations.

The current version supports single-point calculations (SP) using semi-empirical methods (AM1, PM3, PM6, etc.), HF, DFT, and electron-correlation methods (MP2, MP3, MP4, CCSD, CCSD(T)). Additionally, geometry optimization (Opt), frequency (Freq), IR and Raman intensities, zero-point energy, enthalpy, Gibbs free energy, dipole moment, static polarizability, hyperpolarizability, and NMR calculations are also available.

PBC-GEBF

In the PBC-GEBF approach, the ground-state energy per unit cell for molecular crystals or liquids of small molecules can be easily obtained at various theoretical levels. For these systems, molecules are automatically treated as fragments by default. Specifically, PBC-GEBF-X (X = HF, DFT, MP2, CCSD, CCSD(T), etc.) energies can be calculated for the periodic systems mentioned above.

CIM

In the CIM approach, electronic correlation is treated using localized molecular orbitals for both occupied and virtual spaces. For a target molecule, clusters are automatically generated from localized molecular orbitals by the program. The approximate correlation energy of the molecule is then obtained by summing the correlation contributions from a series of independently solved clusters. The current version supports single-point energy calculations and geometry optimization at the CIM-MP2 and CIM-RI-MP2 levels. Additionally, conventional MP2 and RI-MP2 calculations for medium-sized systems are also available.

PBC-CIM

In the PBC-CIM approach, the correlation energy per unit cell of a periodic system is computed as the sum of the correlation contributions from electron-correlation calculations on a series of finite clusters. Each cluster includes a subset of localized Wannier functions (for the occupied space) and projected atomic orbitals (for the virtual space), derived from a periodic HF calculation. Electron-correlation calculations on clusters can be performed using MP2 or CCSD.

References

Publications using GEBF or PBC-GEBF module should cite the following references:

• Li, W.; Dong, H.; Ma, J.; Li, S. Acc. Chem. Res. 2021, 54, 169.
• Li, S.; Li, W.; Ma, J. Acc. Chem. Res. 2014, 47, 2712.
• Li, S.; Li, W.; Fang, T. J. Am. Chem. Soc. 2005, 127, 7215.

Publications using CIM or PBC-CIM module should cite the following references:

• W. Li, Y. Wang, Z. Ni, S. Li. Acc. Chem. Res. 2023, 56, 3462.
• Li, S.; Ma, J.; Jiang, Y. J. Comput. Chem. 2002, 23, 237.

Optional citation for LSQC program:

• Li, S.; Li, W.; Jiang, Y.; Ma, J.; Fang, T.; Dong, H.; Hua, W.; Hua, S.; Guo, Y.; Ni, Z.; Zhao, D.; Li, Y.; Yuan, D.; Liao, K.; Wang, Y.; Hong, B.; Du, J.; Shen, X.; Zheng, Y.; Feng, H.; Lin, J. LSQC Program, Version 3.0. Nanjing University, Nanjing 2025, see https://itcc.nju.edu.cn/lsqc.

The license of GAUSSIAN should be available for you and cited if Gaussian program is employed for subsystems calculations. See http://www.gaussian.com/ for more information.

The license of CRYSTAL should be available for you and cited if CRYSTAL program is employed for PBC-HF calculations in PBC-CIM approach. See  https://www.crystal.unito.it/for more information.

Contacts

LSQC Group:

• Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, P. R. China.
• Email: lsqc@nju.edu.cn
• URL: https://itcc.nju.edu.cn/lsqc